lib/panel/volmon: New panel applet

1 files changed, 97 insertions, 3 deletions

diff --git a/lib/panel/volmon b/lib/panel/volmon
index 0b1b87e..50f6344 100755
--- a/lib/panel/volmon
+++ b/lib/panel/volmon
@@ -1,10 +1,104 @@
 #!/bin/sh
+#
+# volmon -- Panel applet to monitor ALSA mixer volume
+#
+# Copyright (C) 2018  Patrick "P. J." McDermott
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+set -eu
+
+# Default values, overridden in ~/.config/panel/volmonrc
+scontrol='Master,0'
+db_format_on='%3.0f'
+db_format_off='off'
+output='dB Vol:\n${Front_Left} ${Front_Right}\n${Side_Left} ${Side_Right}\n'
+output="${output}"'${Rear_Left} ${Rear_Right}\n'
+
+volmon()
+{
+	local pb_bre=
+	local channel_var=
+	local db_vol=
+	local on_off=
+	local vol_str=
+
+	pb_bre='^  \([^:][^:]*\): Playback [0-9][0-9]* \[[0-9][0-9]*%\]'
+	pb_bre="${pb_bre}"' \[\(-*[0-9][0-9]*.[0-9][0-9]\)dB\] \[\(o[nf]*\)\]$'
+
+	while :; do
+		if ! read -r channel_var; then
+			break
+		fi
+		if ! read -r db_vol on_off; then
+			break
+		fi
+		case "${on_off}" in
+			'on')
+				vol_str="$(printf "${db_format_on}" ${db_vol})"
+				;;
+			'off')
+				vol_str="$(printf "${db_format_off}" ${db_vol})"
+				;;
+		esac
+		eval "${channel_var}=\"\${vol_str}\""
+	done <<-EOF
+		$(amixer get "${scontrol}" | sed -n "
+			/${pb_bre}/{                 # Playback channel lines.
+				h;                   # Save original line.
+				s/${pb_bre}/\1/;     # Extract channel name.
+				s/[^A-Za-z0-9]/_/g;  # Make safe for var name.
+				p;                   # And print it.
+				g;                   # Restore original line.
+				s/${pb_bre}/\2 \3/;  # Extract volume and mute.
+				p;                   # And print it.
+			};")
+		EOF
+
+	eval "printf \"${output}\""
+
+	return 0
+}
+
+usage()
+{
+	printf 'Usage: %s\n' "${0}"
+
+	return 0
+}
 
 main()
 {
-	vol="$(amixer get Master,0 | \
-		sed -n 's/^.*Playback [0-9]* \[\([0-9]*\)%\].*$/\1/p')"
-	printf '🔉%3d%%\n' ${vol}
+	if [ ${#} -ne 0 ]; then
+		usage 1>&2
+		return 1
+	fi
+
+	# POSIX on the dot utility:
+	# "If no readable file is found, a non-interactive shell shall abort"
+	# So to survive an ENOENT or other error, we need this eval/cat command.
+	eval "$(cat ~/.config/panel/volmonrc 2>/dev/null || :)"
+
+	volmon
+
+	return 0
 }
 
 main "${@}"